I’m not sure what you mean here…UE4 is as modular as it gets…I only ever use the bits I need.
It can run quite well on under-powered machines…I have a secondary machine that is 5 to 6 years old that runs the engine fine, it doesn’t even have a core2duo cpu, it’s a dual core pentium (of the early variety) it has a Radion GPU that cost me < 100 quid brand new…It did need a bit more ram though.
This doesn’t happen to me…It only re-compiles if I make any changes to the material and save them
The UI tools are okay aren’t they? what else would you like to see?
The UE4 editor or VS? In any case patience is a virtue…I just loaded up a test project in the editor and it took approx 5-7 seconds…patience is a virtue (or so they say)…